Keyboard with roll-over feature

ABSTRACT

A keyboard has a roll-over feature in that a bistable element (flipflop) is associated with each key. The keys are successively interrogated. When a depressed key is interrogated, the code data thereof is passed on, and the flipflop is set. If the key is interrogated again, the flipflop blocks the passage of the code data. When the key is released, the flipflop is reset.

United States Patent [191 Scholten [451 Dec. 11, 1973 KEYBOARD WITH ROLL-OVER FEATURE [75] Inventor: Johannes Hermanus Maria Scholten,

Emmasingel, Eindhoven,

Netherlands [73] Assignee: U.S. Philips Corporation, New

York, NY.

[22] Filed: Nov. 7, 1972 [21] Appl. No.: 304,388

[30] Foreign Application Priority Data Nov. 17, 1971 Netherlands 15804 [52] US. Cl 340/365 E, 197/98, 340/146.1 AB [51] Int. Cl. G06f 3/02 [58] Field of Search 340/365 E, 365 S,

340/l46.l AB; 307/247 A; 197/98 [56] I References Cited UNITED STATES PATENTS 3,683,370 8/1972 Nagano et al. 340/365 E Primary Examiner.lohn W. Caldwell Assistant Examiner-Robert J. Mooney Att0rneyFrank R. Trifari 5 7 ABSTRACT A keyboard has a roll-over feature in that a bistable element (flipflop) is associated with each key. The keys are successively interrogated. When a depressed key is interrogated, the code data thereof is passed on, and the flipflop is set. If the key is interrogated again, the flipflop blocks the passage of the code data. When the key is released, the flipflop is reset.

2 Claims, 2 Drawing Figures G21 FFZl 121 N 21 B21 K21 DZl -L A21 G22 FFZZ KEYBOARD WITH ROLL-OVER FEATURE The invention relates to a keyboard comprising an interrogation unit by means of which interrogation signals can be generated so that the keys can be interrogated. An interrogation signal enabler code data of a depressed key to appear on an output which is connected to said key. A blocking unit is provided for each key so that requestable code data of a key which is kept depressed, can be allowed to pass under the control of a first interrogation signal, but can be blocked for further interrogation signals. In a keyboard of this kind, in priciple no errors occur when keys are depressed in rapid succession and a next key is already depressed before a previous key is released. A keyboard of this kind is known from l.B.M. Technical Disclosure Bulletin; vol. 13, no. 1, June, 1970, pages 72-73. The described keyboard is actuated at fixed instants by a clock pulse, so that the first monostable multivibrators (detectors) which are associated with all depressed keys are actuated. Each of these monostable multivibrators is followed by second monostable multivibrators, which supply a signal if the associated first monostable multivibrator is set to the active state. The time constant of the first monostable multivibrators is larger than the interval between two successive clock pulses, so that the first multivibrator is set to the active state when the associated key is depressed, and remains in this state until the key is released. It is thus achieved, that the code data of a depressed key is applied only once to a processing unit.

A keyboard of this kind has the drawback that the clock pulses must arrive at regular instants, it being necessary that the processing unit is prepared to receive the code data of newly depressed keys. This imposes problems. First of all, it may be that the processing of code data of different keys requires a different time interval. Depression of the key entitled extract the root from the last number punched", requires considerable time in a calculator. If this time exceeds the time between two successive clock pulses, problems may arrise. It may also be that an installation comprises a large number of keyboards, for example, 64 which are successively interrogated according to the time multiplex principle. If only few of these 64 keyboards are active, the interrogation frequency can be increased for the active keyboards. Finally, it is also possible that the installation comprises other input units which have a high priority. In that case, it is advantageous to interrupt the input from the keyboards for a brief period, for example, for 0.1 second. In all cases, the known keyboard involves problems which are due to the fixed repetition time of the clock pulses. Brief interruptions in the clock pulse can be masked by prolonging the time constant of the first monostable multivibrators, but this makes it objectionable to depress the same key twice in rapid succession. These drawbacks are eliminated according to the invention, which is characterized in that said blocking unit comprises a bistable element which can be set by said first interrogation signal so that a blocking element can be activated, and can be reset after the key has been released so that the said blocking element can be de-activated. The time during which the bistable element is in the blocking state can thus be adapted to the circumstances, while the repetition time of the clock pulse is no longer decisive.

A further drawback of the described keyboard is the construction of the monostable multivibrators, which usually comprise an RC-network. A preferred embodiment according to the invention is characterized in that the keys, which are arranged in rows and columns in the form of a matrix and which are connected by row conductors and column conductors, can be columnwise interrogated by successive driving of the column conductors by the interrogation'device, which is constructed as an integrated circuit together with the blocking units which are row-wise connected to the row conductors. It is easier to incorporate a bistable element (flipflop) in an integrated circuit, than in an RC- network. In a given kind of integrated circuit, the resistors preferably do not have a value higher than a few k0, and capacitors a value not higher than a few 10 farad. In this manner RC-values of, for example, 10 second can be achieved. For a keyboard much higher values might be required, for example 10* second, which gives rise to problems. Furthermore, the combination of interrogation unit and blocking units in a single integrated circuit results in a very compact construction. If each key is furthermore connected to one of the row conductors and one of the column conductors, only few connections are required between the keyboard and the integrated circuit. If the installation comprises a plurality of keyboards, the interrogation unit and the blocking units of all keyboards can be combined so that an additional saving is realized.

. The invention will be described in detail with reference to FIGS. 1 and 2. The FIGS. 1 and 2 illustrate an embodiment according to the invention. FIG. 1 shows a keyboard comprising six keys K11, K12, K13, K21, K22, and K23. It also comprises a clock CL and a counter T, two column conductors C1 and C2, and three row conductors R1, R2, and R3. The remaining components are numbered correspondingly like the keys, i.e. for the key K11, there are three logic AND- gates A11, G11 and N11, an inverter I11, a diode D11, a bistable element F11, and an output terminal B11. The clock CL supplies clock pulses either independently or under the control of an external unit not shown. The counter T and the clock CL constitute the interrogation unit. The counter T is set to a subsequent position by each clock pulse, a positive pulse each time appearing on one of the outputs. To this end, these outputs can comprise a differentiating element. Assume that the key K11 is depressed, so that a connection is established between the two contacts of this key. This may be a galvanic connection, but may also be a capacitive coupling, or the like. The AND-gate A11 then receives two positive signals and supplies one positive pulse. When the bistable element FF11 is in the rest state, its 1-output is high, and the AND-gate N11 receives two high signals. As a result, a higher signal is applied to the output terminal B11. This signal acts as the said code data and can subsequently be decoded in a decoder (not shown) before being further processed. The output signal of the AND-gate N11 is returned to an input of the bistable element FF11, so that the latter is set to the active state. As a result, its 1"-output becomes low, so that the AND-gate N11 is blocked. When the column conductor C11 is driven again, no further pulse appears on the output terminal 811.

When the key K11 is released and the column conductor C1 is again driven by a high signal, the AND gate A11 receives only one high signal, so it does not supply a high signal on its output. AND-gate G11 receives a signal from the column conductor C1. The output of the inverter 111 also supplies a high signal, so that AND-gate G11 supplies a high signal. The bistable element FF11 is thereby reset to the reset state. As a result, its l-output becomes high, and the blocking of the AND-gate N11 is eliminated. However, if the AND-gate A11 supplies a high signal, this signal is inverted in the inverter Ill so that the output thereof becomes low. This prevents resetting of the bistable element FF11.

The circuit furthermore comprises the row conductors R1 3. These conductors are actually not always required. However, if the blocking units and the interrogation unit are arranged at a distance from the keys (for example, in an integrated circuit), only few connections must then be made to the keys, i.e. for each row there is only one row conductor, and for each column only one column conductor. This is described with reference to FIG. 2. Assume that key K21 is depressed after key K11, while key K11 remains depressed. When the column conductor C1 is driven, the AND-gate N11 does not supply a high signal, which is due to the blocking action of thebistable element FFll. The drive pulse (interrogation pulse) on the column conductor C1 is supplied to an input of the AND-gate A21 via the row conductor R1. However, this pulse is further blocked by the diode D21 so that it has no further effect. In given cases the diodes can be omitted, for example, if the interrogation signal is attenuated by a depressed key. Assume that the interrogation pulse has an amplitude of l volt and that the attenuation is 50 percent. In that case, the AND-gate All receives a pulse of 1 volt, and one of 95 volt from the interrogation pulse on C1, and the AND-gate A21 receives one pulse of volt (directly via R1) and one of V4 volt (attenuated again by the depressed key K21). At a given proportioning, the ANDgate 21 will not supply a high output signal in such a case.

FIG. 2 shows a keyboard comprising sixteen keys K11 .K44, which are separately shown in the actual keyboard KB for the sakeof clarity. The device furthermore comprises an integrated circuit LSI, which comprises 16 modules M11 M44, one each for the correspondingly numbered keys, and the interrogation unit AV. The modules comprise the blocking units and are as described with reference to FIG. 1. The module M11 comprises, for example, the bistable element FFll, the AND-gate All, G11 and N11, and the inverter Ill. A diode is associated with each key as is shown in FIG. 1. Eight connections exist between the keyboard KB and the integrated circuit, i.e. the column conductors C1 4, and the row conductors R1 4. This number need not be large even in the case of many keys: for example, for 64 keys, only 16 connections are required, i.e. eight row conductors and eight column conductors. The row conductors are connected to the modules via the relevant inputs of the AND-gates A11 44 (ie the lower input in FIG. 1); the column conductors are not only connected to a contact of the keys of the relevant column, but also to the modules, via the relevant inputs of the AND-gates All 44 and G11 44 (each time the upper inputs of FIG. 1). The output terminals of the modules M11 44 can be connected to inputs of a decoder, which converts the code data into a code, for example, a parallel or series-binary code. In the former case, four conductors are required for 16 keys, while six conductors are required for 64 keys. This number of conductors is small and can be readily realized in an integrated circuit. Consequently, it is advantageous to construct the decoder, the interrogation unit, and the modules, together as an integrated circuit.

The invention also relates to other embodiments of the keyboard, for example, using other types of gates in the blocking units. It is alternatively possible to use other types of keys, for example keys having a break contact. However, the code data of a key which is depressed, and which is kept depressed, is always passed on only once.

I claim:

l. A keyboard with a roll-over function comprising:

a plurality of keys;

an interrogation unit connected to said keys for generating interrogation signals for interrogating said keys, said interrogation signals enabling code data of respectively depressed keys to appear upon outputs connected to each of said keys; and

a blocking unit connected to and associated with each key for allowing requestable code data to pass under control of a first interrogation signal when a key is kept depressed, but which blocks said code data under the influence of further interrogation signals, each blocking unit having a bistable element which is set by said first interrogation signal, and a blocking element which is activated thereby and which is resettable after a depressed key is released, so that it can be de-activated.

2. A keyboard as claim 1, wherein the keys are arranged in rows and columns in the form of a matrix and are connected by row conductors and column conductors said keys being capable of columnwise interrogation by successive driving of the column conductors by the interrogation unit, said interrogation unit being constructed as an integrated circuit together with the blocking units which are row-wise connected to the row conductors. 

1. A keyboard with a roll-over function comprising: a plurality of keys; an interrogation unit connected to said keys for generating interrogation signals for interrogating said keys, said interrogation signals enabling code data of respectively depressed keys to appear upon outputs connected to each of said keys; and a blocking unit connected to and associated with each key for allowing requestable code data to pass under control of a first interrogation signal when a key is kept depressed, but which blocks said code data under the influence of further interrogation signals, each blocking unit having a bistable element which is set by said first interrogation signal, and a blocking element which is activated thereby and which is resettable after a depressed key is released, so that it can be de-activated.
 2. A keyboard as claim 1, wherein the keys are arranged in rows and columns in the form of a matrix and are connected by row conductors and column conductors said keys being capable of columnwise interrogation by successive driving of the column conductors by the interrogation unit, said interrogation unit being constructed as an integrated circuit together with the blocking units which are row-wise connected to the row conductors. 